• Title/Summary/Keyword: Non-contact Mode

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Non-contact Ultrasonic Technique for the Evaluation Wall Thinning of the Plate (박판의 두께감육 평가를 위한 비접촉 유도초음파 검사 기법)

  • Park, Ik-Keun;Kim, Hyun-Mook;Kim, Tae-Hyung;Kim, Yong-Kwon;Cho, Yong-Sang;Song, Won-Joon
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.4
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    • pp.287-293
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    • 2005
  • Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of defects thinning simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of defects thinning. Measurement of the mode group velocity can be also used to quantify depth thinning.

Contact buckling behaviour of corrugated plates subjected to linearly varying in-plane loads

  • Dong, Jianghui;Ma, Xing;Zhuge, Yan;Mills, Julie E.
    • Steel and Composite Structures
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    • v.29 no.3
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    • pp.333-348
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    • 2018
  • An analytical method is developed for analysing the contact buckling response of infinitely long, thin corrugated plates and flat plates restrained by a Winkler tensionless foundation and subjected to linearly varying in-plane loadings, where the corrugated plates are modelled as orthotropic plates and the flat plates are modelled as isotropic plates. The critical step in the presented method is the explicit expression for the lateral buckling mode function, which is derived through using the energy method. Simply supported and clamped edges conditions on the unloaded edges are considered in this study. The acquired lateral deflection function is applied to the governing buckling equations to eliminate the lateral variable. Considering the boundary conditions and continuity conditions at the border line between the contact and non-contact zones, the buckling coefficients and the corresponding buckling modes are found. The analytical solution to the buckling coefficients is also expressed through a fitted approximate formula in terms of foundation stiffness, which is verified through previous studies and finite element (FE) method.

Identification of Guided-wave Modes for on-line monitering in the pipe weldment (배관 용접부의 상시감시를 위한 유도초음파 모드 규명)

  • Park Ik-Geun;Kim Tae-Hyeong;Lee Cheol-Gu;Kim Yong-Gwon;Park Tae-Seong;Lee Jin-Hyeok
    • Proceedings of the KWS Conference
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    • 2006.05a
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    • pp.307-309
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    • 2006
  • For efficient NDE of pipes, essential components of power plant facilities, ultrasonic guided waves were generated and received applying an air-coupled transducer and comb one as non-contact technology, Mode generation and selection were predicted based on theoretical dispersive curve and the element spaceof a comb transducer. In addition, a receiving angle of the air-coupled transducer was determined to acquire the predicted modes by theoretical phase velocity of each mode. Theoretical dispersive curve was compared with the results of the time-frequency spectroscopes based on the wavelet transform and 2D-FFT to identify the characteristics of the received mode. The received modes show a good agreement with the predicted ones.

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Vibration Analysis of Bladed Disk using Non-contact Blade Vibration System (비접촉 진동측정 시스템을 이용한 블리스크의 진동분석)

  • Joung, Kyu-Kang;Kim, Myeong-Kuk;Park, Hee-Yong;Chen, Seung-Bae;Park, Noh-Gill
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.132-139
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    • 2008
  • The blade vibration problem of bladed disk is the most critical subject to consider since it directly affects the stable performance of the engine as well as life of the engine. Especially, due to complicated vibration pattern of the bladed disk, more effort was required for vibration analysis and test. The research of measuring the vibration of the bladed disk, using NSMS(Non-intrusive stress measurement) instead of Aeromechanics testing method requiring slip ring or telemetry system with strain gauge, was successful. These testing can report the actual stresses seen on the blades; detect synchronous resonances that are the source of high cycle fatigue (HCF) in blades; measure individual blade mis-tuning and coupled resonances in bladed disks. In order to minimize the error being created due to heat expansion, the tip timing sensor is installed parallel to the blade trailing edge, yielding optimal result. Also, when working on finite element analysis, the whole bladed disk has gone through three-dimensional analysis, evaluating the family mode. The result of the analysis matched well with the test result.

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Vibration Analysis of Bladed Disk using Non-contact Blade Vibration System

  • Joung, Kyu-Kang;Han, Chak-Heui;Kang, Suk-Chul;Kim, Yeong-Ryeon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.871-876
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    • 2008
  • The blade vibration problem of bladed disk is the most critical subject to consider since it directly affects the stable performance of the engine as well as life of the engine. Especially, due to complicated vibration pattern of the bladed disk, more effort was required for vibration analysis and test. The research of measuring the vibration of the bladed disk, using NSMS(Non-intrusive stress measurement) instead of Aeromechanics testing method requiring slip ring or telemetry system with strain gauge, was successful. These testing can report the actual stresses seen on the blades; detect synchronous resonances that are the source of high cycle fatigue(HCF) in blades; measure individual blade mis-tuning and coupled resonances in bladed disks. In order to minimize the error being created due to heat expansion, the tip timing sensor is installed parallel to the blade trailing edge, yielding optimal result. Also, when working on finite element analysis, the whole bladed disk has gone through three-dimensional analysis, evaluating the family mode. The result of the analysis matched well with the test result.

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Preliminary Study of the Measurement of Foreign Material in Galvanic Corrosion Using Laser Ultrasonic

  • Hong, Kyung Min;Kang, Young June;Park, Nak Kyu;Choi, In Young
    • Journal of the Optical Society of Korea
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    • v.17 no.4
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    • pp.323-327
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    • 2013
  • A laser ultrasonic inspection system has the advantage of nondestructive testing. It is a non-contact mode using a laser interferometer to measure the vertical displacement of the surface of a material caused by the propagation of ultrasonic signals with the remote ultrasonic generated by laser. After raising the ultrasonic signal with a broadband frequency range using a pulsed laser beam, the laser beam is focused to a small point to measure the ultrasonic signal because it provides an excellent measurement resolution. In this paper, foreign materials are measured by a non-destructive and non-contact method using the laser ultrasonic inspection system. Mixed foreign material on the corroded part is assumed and the laser ultrasonic experiment is conducted. An ultrasonic wave is generated by pulse laser from the back of the specimen and an ultrasonic signal is acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer (CFPI). The characteristic of the ultrasonic signal of existing foreign material is analyzed and the location and size of foreign material is measured.

Hand Motion Signal Extraction Based on Electric Field Sensors Using PLN Spectrum Analysis (PLN 성분 분석을 통한 전기장센서 기반 손동작신호 추출)

  • Jeong, Seonil;Kim, Youngchul
    • Smart Media Journal
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    • v.9 no.4
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    • pp.97-101
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    • 2020
  • Using passive electric field sensor which operates in non-contact mode, we can measure the electric potential induced from the change of electric charges on a sensor caused by the movement of human body or hands. In this study, we propose a new method, which utilizes PLN induced to the sensor around the moving object, to detect one's hand movement and extract gesture frames from the detected signals. Signals from the EPS sensors include a large amount of power line noise usually existing in the places such as rooms or buildings. Using the fact that the PLN is shielded in part by human access to the sensor, signals caused by motion or hand movement are detected. PLN consists mainly of signals with frequency of 60 Hz and its harmonics. In our proposed method, signals only 120 Hz component in frequency domain are chosen selectively and exclusively utilized for detection of hand movement. We use FFT to measure a spectral-separated frequency signal. The signals obtained from sensors in this way are continued to be compared with the threshold preset in advance. Once motion signals are detected passing throng the threshold, we determine the motion frame based on period between the first threshold passing time and the last one. The motion detection rate of our proposed method was about 90% while the correct frame extraction rate was about 85%. The method like our method, which use PLN signal in order to extract useful data about motion movement from non-contact mode EPS sensors, has been rarely reported or published in recent. This research results can be expected to be useful especially in circumstance of having surrounding PLN.

Measurement of Dynamic Elastic Modulus of Foil Material by ESPI and Sonic Resonance Testing (ESPI와 음향공진법을 이용한 Foil 재료의 동적탄성계수 측정)

  • Lee H.S.;Kim K.S.;Kang K.S.;Ahmad Akhlaq
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.914-917
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    • 2005
  • The paper proposes a new sonic resonance test for a dynamic elastic constant measurement which is based on time-average electronic speckle pattern interferometry(TA-ESPI)and Euler-Bernoulli equation. Previous measurement technique of dynamic elastic constant has the limitation of application for thin film or polymer material because contact to specimen affects the result. TA-ESPI has been developed as a non-contact optical measurement technique which can visualize resonance vibration mode shapes with whole-field. The maximum vibration amplitude at each vibration mode shape is a clue to find the resonance frequencies. The dynamic elastic constant of test material can be easily estimated from Euler-Bernoulli equation using the measured resonance frequencies. The TA-ESPI dynamic elastic constant measurement technique is able to give high accurate elastic modulus of materials through a simple experiment and analysis.

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A study on the design of the laser marking system using galvanometer scanner (갈바노미터 스캐너를 이용한 레이저 마킹 시스템 설계 제작에 관한 연구)

  • 조태익;이건이
    • 제어로봇시스템학회:학술대회논문집
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    • 1986.10a
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    • pp.145-148
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    • 1986
  • To perform the marking on metal with high speed and non-contact using the laser beam of high energy, laser marking system is designed and fabricated applying the galvanometer scanner capable of high speed-precise beam positioning controlled by microprocessor. Laser is a Q-switched Nd:YAG producing multi-mode, wavelength, 1060nm. Optical system is composed of beam expander, scanning mirror and flat field lens. Consequently, the laser marking is satisfactorily achieved regardless of kinds of metal.

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ESPI를 이용한 에어콘용 시로코팬의 신뢰성평가

  • 김경석;강기수;양승필
    • Proceedings of the Korean Reliability Society Conference
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    • 2002.06a
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    • pp.253-260
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    • 2002
  • This paper propose Electronic Speckle Pattern Interferometry(ESPI) for reliability evaluation of electronic device. Especially, vibration problem in a fan of air conditioner, motor of washing machine and etc. is important factor to design the devices. However, it is difficult to apply previous method, accelerometer to the devices with lightweight and complex geometry. ESPI, non-contact measurement technique is applied for vibration analysis of a sirocco fan inside air conditioner. Vibration mode shapes, natural frequency and the range of the frequency are decided and compared with that of FEM analysis. In mechanical deign of new product, ESPI is able to supply effective design information.

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